Generally, different forms of light can be used in many different applications. Through the delivery of specific wavelengths of light, effects such as the inactivation of bacteria, fungi, or viruses can be accomplished, chemical reactions, such as the curing of plastics or other materials can be caused, heat can be generated, and the wavelength of the light can be converted to an alternative wavelength.
White light is generally composed of multiple wavelengths of light from across the visible spectrum. White light is generated though perception of the human eye by the sensitization of the S, M and L cones (short, medium, and long, respectively) which react to wavelengths most commonly described as blue, green, and red, respectively. By having a light source generating wavelengths in each of these cones at proper intensities, white light is perceived by the human eye. To perceive white light, all three cone types must be stimulated.
Typically, a minimum of three colors across the visible spectrum must be used to stimulate the three cone types, as in, for example, of red, green, and blue (RGB) color mixing to produce white light. Additional methods of color mixing, such as blue light pumped phosphors, using two sources of light, one in the blue range, and an additional phosphor that creates light across multiple colors can also accomplish appropriate stimulation of the three cone types, to be perceived as white light. The addition of other wavelengths of light can improve the color rendering index (a rating of quality associated with white light).
Some specific wavelengths of visible light can be used for active reasons beyond general illumination. For example, activation of fluorescent materials can be achieved with approximately 400 to approximately 420 nm range, similar to UVA, or a “black light,” curing of plastics can be achieved with approximately 380 to approximately 420 nm light, heat delivery can be achieved with near-infrared approximately 650 to approximately 700 nm light, and inactivation of bacteria can be achieved with near-infrared approximately 650 to approximately 700 nm light. As used herein, unless otherwise specified, approximately can include plus or minus 5 nm.
Regarding inactivation of bacteria, the United States Center for Disease Control (CDC) has reported that every year, 1.7 million hospital patients (about one in every twenty admitted) contract a hospital-acquired infection (HAI) in the United States from bacterial, viral, or fungal microorganisms. These infections result in almost 100,000 deaths, 35-45 billion US$ in excess costs and 25.9 million wasted patient bed days due to the excess costs and time associated with HAIs. Because these infections are deemed “preventable” by the CDC and the US Medicare system, costs associated with such HAIs fall directly on the hospitals. Of hospitals nationwide, 78% have what the CDC considers an infection problem with the rates of infection they see annually. Additionally, in the 16,000 nursing homes in the US, the problem is similar.
In addition to those direct operating costs, current and emerging government regulations (such as the Affordable Care Act) and standards of care are demanding reductions in infections across the nation, yet existing practices and products are still lacking in efficacy. Starting in 2014 the US Affordable Care Act will impose 1-3% reductions in US Medicare reimbursements to hospitals that do not meet appropriate infection standards. Similar regulations may exist in other countries.
Hospital reputation is also becoming increasingly transparent with publicly available data allowing consumers to make decisions about hospitals. Infection rates are publicly available for most hospitals in the US; a hospital with high infection rates may drive away potential “customers.” Serious litigation costs in severe cases can also add to the ‘price’ of infections acquired in a healthcare facility.
Environmental contamination in hospital environments is a key factor in the source of these HAIs, among others. Current methods of attacking environmental contamination range widely, from traditional mopping and surface cleaning to the use of burst ultraviolet (UV) and hydrogen peroxide vapor. Yet, in full force application, infections are still a reality in almost every hospital.
In the cultivation of livestock and agricultural products, contamination from bacteria, fungi, or viruses can cause losses of animal life, plant life, and/or spoilage of rendered products. Common production practices now pack animals and plants densely for efficiency, in terms of space and finances, yet contamination from microorganisms can spread rapidly in such an environment, with infection spreading between plants or animals.
Currently, there is extensive use of pesticides, antibiotics, and chemical cleaners to prevent loss of final product by preventing contamination of animals or agriculture products, yet animal and plant losses, final product losses, and the unknown distribution of contaminated final products is still an issue faced by the industry. Thus, there is a continuing need for better methods to control microorganisms in the cultivation environment and processing facilities to prevent loss of final product.
In the retail sale of food, fresh products are commonly displayed to customers in the shopping environment. In many retail stores, the products are stored on shelves and in cases with viewing windows. Many of these products are considered perishable, with a very short shelf life like meat, produce, or fish. The short shelf life of these items is due to the degradation of the quality of the product over the time displayed. This degradation of the product is caused by a variety of factors: breakdown of cells or molecules due to aging, loss of water or other volatile components into the air, or spoilage based on bacterial, fungal, or viral contamination.
Controlled environments are required for many purposes, such as the preservation of food products, the aging of goods, such as wines, liquors, and tobacco products, or the general prevention of contamination during many industrial processes. Such environments are protected and controlled in many different manners, including in terms of air quality, temperature, humidity, and particle count.
Perishable food is commonly stored in refrigerated enclosures to slow degradation of the food and to slow bacterial growth that can cause food spoilage and food sickness. While refrigeration alone can extend food life and quality, compared with room temperature storage, bacteria and molds can still be common destroyers of food in these environments, in a home refrigerator just as in an industrial meat locker.
Humidors are humidity controlled environments, commonly associated with the storage or aging of cigars and tobacco products, that maintain moisture content at a set level for the items stored in the enclosure. However, bacterial and mold spoilage of these goods can occur in the event of contamination, resulting in the loss of what is typically a high value product.
In clean rooms, efforts are made to control the amount of particles in the air in a given enclosure. Most function by continuously pumping in filtered air and forcing the exodus of airborne particles. Bacterial growth and the generation of bacteria or mold spores from contaminated sites can continuously generate particles in the environment that can be difficult to prevent and cause costly contamination issues in high-value products undergoing processing or storage in the environment.
In a food preparation environment (e.g., restaurants, industrial kitchens, fast food, prepared goods store, for direct sale or delivery to the consumer/customer) bacteria, fungi, and/or viruses pose issues of spoilage, pathogenic contamination, and infection, and can be a serious issue for the establishment. These contamination issues can come from a large variety of sources in such an open environment: e.g., personnel, customers, raw materials, air systems, and water. While many cleaning practices have typically been implemented at these sites, contamination and infection outbreaks are still seen. Typically, these contamination issues are only noticed after the damage is done, when inventory is spoiled or customers are sick.
UV light can be used for disinfection in an industrial environment, but not in environments where personnel would also be exposed to the light, for safety reasons. This greatly limits the ability to create a consistently protected environment against bacteria. UV light also has known detrimental effects on plastics, proteins, and DNA, potentially degrading goods, raw materials, packaging, and equipment in the industrial environment.
Loss of goods and raw materials occurs in many industrial processes because of bacterial, viral, or fungal infections or contamination, including, but not limited to, pharmaceuticals, brewing/distillation, food production, food packaging, chemical processing, and semiconductor processing steps requiring a clean room environment.